1. Field of the Invention
This invention relates to techniques for using a gas stream to conrol an environment and pertains in particular to methods for controlling temperature and other characteristics of the gas stream.
2. Description of the Prior Art
Temperature control of a gas stream is typically achieved through an interface where the gas stream and the heat source or sink interact. Heretofore, however, the interface has been of limited application. For example, in the conventional hot air furnace system, the interface is a metal plenum which readily exchanges heat, but is incapable of other functions. That is, it does not readily lend itself to chemical or other simultaneous treatment of the gas stream.
Accordingly, one object of this invention is to achieve gas stream heat exchange in a way which is simple yet capable of simultaneously performing other functions.
Gas streams are used in a wide variety of ways to control environment, but a particularly important application is in the treatment of medical patients. When it is necessary to control the respiration of a medical patient as, for example, during a surgical procedure in which anesthesia is being administered, the patient should breathe in a controlled environment. If the environment in which the patient breathes is part of a conducted system, the atmosphere becomes a gas stream which can be treated to control the constituents thereof such as oxygen, carbon dioxide, nitrous oxide, other anesthetic vapors and the like.
While breathing systems are available in which the constituency of the gas stream is controllable, such systems are not readily amenable to control of the gas stream temperature. Consequently, the gas stream often reaches the patient at much less than body temperature thereby necessitating the application to the patient of external heat in order to avoid dangerous drops in body temperature.
Accordingly, another object of this invention is to maintain the temperature of a gas stream reaching a patient's respiratory tract within a physiologically beneficial range.
Regulating the heat of a gas stream in such systems, however, is not a simple matter. Where the environment and the gases are temperature sensitive, for example, safety code limitations must not be exceeded. Moreover, once a patient has been placed in the system and system pressures are stabilized, pressure changes must be avoided which would adversely interfere with established breathing patterns. That is, any regulation of the gas stream may not interfere with the spontaneous or assisted respiration of the patient or with conventional techniques of administering anesthesia.
Accordingly, another object of this invention is to achieve safe, simple and efficient temperature control of the gas stream without disturbing established practices.